The terms “spray painting”, “spray coating”, and “spraying” are used to refer to the formation of an aerosol by accelerating a liquid stream in a region where it experiences abrupt expansion. One way to achieve this expansion is to force a fluid through an orifice. The velocity of the fluid as it exits the orifice causes the fluid to break-up into droplets. Another method of forming an aerosol directs fluid onto a rotating disk. The fluid is accelerated to the speed of the disk as it moves to the outside of the disk. The velocity of the fluid as it leaves the disk causes the fluid to abruptly expand and break into droplets. These methods create fast-moving sprays traveling on the same vector as the originating fluid. Air jets are frequently positioned near the point where the droplets form to adjust the shape of the spray as it moves along the trajectory established by the original velocity vector.
Some particles traveling at high velocities tend to not wet a target surface. Instead, the droplets bounce off the target surface and are wasted or deposited elsewhere. The droplet deflected from a surface can move unpredictably to other areas of the target, causing variation in coating thickness and surface defects. The air jets associated with these types of spray processes can control the shape of the spray, but have little control over the direction of the droplets, which is established by the direction of the originating fluid. To spray coatings with a consistent thickness over a large area, the spray nozzles are mounted on mechanical systems. Some mechanical systems are programmed to move the spray nozzle(s) through a designated path to yield optimal coating thickness and consistency.
Spray aerosols are used in applications such as spray painting. However, using a spray aerosol to apply films to optical components, such as display panels, often results in a layer with a total thickness variation that undesirably degrades the performance of the optical component.
Examples of optical components that it is desirable to coat with a uniform polymer layer include various types of displays, such as cathode ray tubes, monochrome liquid crystal displays (“LCDs”), color LCDs, and plasma display panels (“PDPs”). Some display panels include color balancing, electric shielding, and/or contrast enhancing features. For example, in a PDP inert gases, such as helium, neon, argon, xenon and mixtures thereof are sealed in a glass envelope (e.g. between two glass panels). A high voltage is applied to selected areas of the display to locally form plasma, which emits light. PDPs, which are also known as gas display panels, have desirable features, such as a wide viewing angle, a slim form, and are active (i.e. light emitting) displays. PDPs are increasingly used in high-quality television sets, including large-format television sets. The advances in PDPs in general are promoting their use in other applications.
Unfortunately, neon, which is often used in the gas mixture for PDPs, produces orange-red light at 585 nm, which can cause an imbalance in the color of the display and reduce contrast unless corrective measures are taken. One technique that has been used balance the color from neon-containing PDPs is to incorporate a notch filter to absorb light around 585 nm. Filters for removing excess light at 585 nm, which also enhance contrast, have been incorporated in PDPs in a number of ways. Techniques include mixing a 585 nm absorbing dye into the adhesive used to laminate elements in the PDP assembly and of applying a polyester film with an appropriate dye to a PDP assembly.
One or more films can be formed from a mixture of dye or dyes in a polymer matrix by any of several suitable techniques, such as solvent casting, extrusion, spray coating, roller coating, dip coating, brush coating and spin coating. However, some of these techniques do not result in a uniform thickness of the dyed layer, resulting in poor optical performance. Thickness variation is particularly difficult to control on large-format substrates, such as are used in television sets. Other techniques, such as laminating a dyed polymer film to a PDP assembly, are expensive and require extra handling and parts. It is desirable to provide methods of applying uniform polymer coatings to glass panels and similar objects, particularly large-format objects. It is further desirable to include a dye or dyes to provide a polymer coating with optical filtering properties. It is yet further desirable to provide polymer coatings with antireflective surfaces.